Spray gun air cap



May 1, 1956 D. J. PEEPS 2,743,963

SPRAY GUN AIR CAP Filed May l1, 1954 BY Mea/W ATTI.

United' States Patent() SPRAY GUN. AIR CAP Donald J. Peeps, Toledo, Ohio, assignor to The De Viibiss Company, Toledo, Ohio, a corporation of Ohio Application May 11, 1954, Serial No. 428,915

4 Claims. (Cl. 299-140.1)

This invention relates to an air cap for a spray gun and particularly to retaining and sealing means therefor.

In order that the fan shaped discharge of a spray gun may be directed in any desired plane, it is the general practice to have the air cap revolvable on the spray vgun. This ,is usually accomplished by having complementary shoulders on the air cap and on a coupling nut which is threaded to the spray gun body. The air cap seats upon and is axially centered by an inner iluid tip r liquid nozzle.

Two main divisions of compressed air are channeled through the air cap. One part of the air is delivered to the ports in the horns and is used to form the atomized material into its ilnal fan shape. This part of the air is usually guided to the horns by an annular passage exteriorly defined in part by the air cap coupling nut. The other main division of the air travels through the more central portionv of the air cap to the atomizing oriiice surrounding the discharge opening of the lluid tip. The seating contact of the air cap with the iluid tip maintains the separate paths for the two divisions of air.

To avoid air leakage through the joint between the air cap and the coupling nut, air caps are sometimes provided with two axially spaced annular seating areas contacting the fluid tip with a path between them for the horn air arriving from ports through the lluid tip. The latter then has more centrally located passages for the air delivered to the center atomizing oriilce of the air cap. f

Such seating areas between the air cap and fluid tip must be carefully made of tapered or other form to insure eifective sealing action and this construction is therefore expensive.

In order that a coupling nut may be slipped over an air cap, the air horns must not extend laterally to a greater dimension than the inner diameter of the coupling nut. For some purposes however better spray formation is obtained with more widely separated horns. One method of forming an air cap with more widely spread horns involves making the horns on a separate ring which is soldered or brazed to the central part of the air capl after the central part has been slipped through the coupling nut. This, of course, requires more work than making the air cap in a single piece.

The principal object of this invention is the provision of simple but effective means for rotatably retaining and sealing an air cap without the use of two seats between the air cap and iluid tip and the provision of retaining means which do not require that the air cap be made in two parts when the hornsV are widely spaced.

This double object is attained by utilizing in combination a split retaining ring between the air cap and coupling nut in place of integral complementary shoulders, and associated with the split ring an O-ring loosely positioned between adjacent coaxial cylindrical surfaces of the air cap and coupling nut with the forward face of the O-ring held in sealing contact, by the pressure of the air going to the horns, upon an annular opening between adjacent coplanar radial surfaces of the air cap and coupling nut.

ICC

2 The peripheral looseness of the 0-ring permits the easy turning of the air cap for any desired positioning of the discharge fan pattern. This ease of rotation would not exist if the O-ring were used conventionally in radially compressed form to seal between coaxial cylindrical surfaces. f

Other objects and advantages of the inventionwill be apparent from the following description and the accompanying drawings, in which, y

Figure 1 is a vertical section of the forward end of a spray gun embodying my invention;

Figure 2 is a horizontal section thereof; and

Figure 3 is an enlarged section taken on the line 3 3 of Figure 2.

As-shown inthe drawings the embodiment of my invention comprises the forward end of a spray gun body 1, with an air cap 2 held upon the body of the coupling nut 3. From the spray material inlet 4 there is a material passage 5 leading into the central bore 6 of the body insert 7. Threaded upon the forward end of the insert 7 is the iluid tip 8 with its restricted outlet 9 under control of the needle valve 10. Held against the end of the spray gun body by the skirt 11 of the iluid tipl 8 is the air partitioning baille 12. As may be seen in Figure 2 the collar 13 of this baille is bent inwardly at 14 to guide the air from duct 15 to the exterior of the collar and bent outwardly at 16 to direct the air from passage 17 interiorly of the collar. Y

The air from duct 15 accordingly proceeds forwardly between the baille 12 and the coupling nut 3, and the iluid tip skirt 11 and the coupling nut, thisl air then travels past the main portion of the iluid tip, in the spacing between the flats of the hexagon outline of the iluid tip and the adjoining circular shape of the air cap, to passages 18 in the air cap 2 leading to the outlet ports 19 in the air cap horns 2i). j

The air from passage 17 turned inwardly by the portion of the collar at 16 travels forwardly within the baille 12 and interiorly ofthe iluid tip skirt 11 to bores 21 in the iluid tip. This air then enters space 22 between the tip and air cap to be discharged from the center orifice 23 of the air cap.

The air cap 2 and the coupling nut 3 are permanently and rotatably joined by the splitring 24. Such an assembly permits the air cap to be constructed with the wide horns 20 which would not allow the air cap to be inserted through the coupling nut for the use of integral complementary shoulders.

Rearwardly of the location of the split ring 24 an O- ring 25 s positioned within the square cornered groove 26 in the coupling nut 3 with the inner periphery of the O-ring upon the reduced end 27 of the air cap 2. The reduced end 27 is terminated forwardly by the shoulder 28 which is ilush and coplanar with the forward side 29 of the groove 26.

The spacing of the bottom of the groove 26 from the surface of the reduced end 27 of the air cap 2 and the thickness of the O-ring are so selected that there is no binding action upon the -Oring by these spaced cylindrical surfaces. This comparative looseness of the O-ring permits it to be thrust forwardly by air pressure, when air is ilowing through the spray gun, into sealing relation over the joint between the adjacent edges of the shoulder 28 on the air cap 2 and the forward side 29 of the groove 26 in the coupling nut 3. f

It is apparent therefore that when the spray gun is idle with no air flowing the air cap may be freely turned in relation to the coupling nut with no interference from the split ring or the O-ring and that when the spray gun is in operation the joint between the air cap and the coupling nut is effectively sealed.

From the foregoing it is also apparent that the inven- 3 tion provides a compact, inexpensive construction which iswasily` assembled and one which efctii'lelyv seals the air cap, while leaving it freely rotatable and permits the use of horns with any desired spread. n

Having thus described my invention what I claim is:

1. In an air. cap for a spray sur), a main body member, horns on the` forward end of the member, said`horns ported for the discharge of spray shaping air jets, a coupling nut constituting in part the outer wall of an air passage to` the horns, the coupling nutl at its forward end engaging the member and threaded at its rearward end to hold the air cap on the spray gun, air passable retaining means rotatably connecting the body member to the coupling nut, an O-ring adjacent to the retaining means, radially. spaced cylindrical surfaces on the body member and the coupling nut between which the O-ring is loosely lodged and adjoining coplanar radial surfaces of the body member and .the `coupling nut against the adjacent edges of which the forward face of the O-ring is held in sealing relation by the ow of air to the horns to prevent any leakage of air from the connection between the body member and the coupling nut.

`2. An air cap yaccording to claim l in which the horns are laterally spread a distance greaterV thanuthe interior diameter of the coupling nut.

3. An air cap according to claim 1 in which the retaining means is a split ring' located forwardly of the O-ring.

4." In an air cap for a spray gun, a main body member, horns on the forward end of the member, said horns ported for the discharge of spray shaping air jets, a coupling nut constituting in part the outer wall of an air passage to the horns, the coupling nut at its forward end engaging the member and threaded at its rearward end to hold the air capf on the spray gun, air passable retaining means rotatably connecting the body member to the coupling nut, an O-ring adjacent to the retaining means, radially spaced cylindrical surfaces ori` the` body member and the coupling nut between which the O-ring is loosely lodged and adjoining, coplanar shoulder means on the body member and the coupling nut forwardly of the cylindrical surfaces against VVwhich the forward face of the O-ring is held in sealing relation by the ow of air to the horns.

References Cited in the le of this patent UNITED STATES PATENTS 2,235,708 Jenkins Mar. 18, 1941 2,249,771 MacMartin July 22, 1941 2,453,597 Sarver Nov. 9, 1948 

